Farm Equipment - RC Dishes Pistons

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RC Dishes Pistons

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=193231
Printed Date: 19 Aug 2025 at 11:33pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: RC Dishes Pistons

Posted By: AaronSEIA
Subject: RC Dishes Pistons
Date Posted: 01 Feb 2023 at 6:42pm

Had to pull the head on my boys RC to diagnose a stuck valve. Was surprised to find dishes pistons. They are flat around the edge for maybe 1/4", then have a dish in them. Not shaped at all like an M&W or Power Crater piston. Any idea who's aftermarket piston they are and what the compression might be?

AaronSEIA

Replies:

Posted By: PaulB
Date Posted: 01 Feb 2023 at 7:35pm

Those are the pistons that would have been installed for a kerosene engine at the Allis factory. Are they Iron pistons? Many of the earliest pistons were iron, not aluminum. The C/R would most likely be 4.71:1 or 4.75:1.

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If it was fun to pull in LOW gear, I could have a John Deere.
Real pullers don't have speed limits.
If you can't make it GO... make it SHINY

Posted By: AaronSEIA
Date Posted: 03 Feb 2023 at 5:51am

Pistons are magnetic. Block is an RC block with a G code. Shifter is completely wore out but the sleeves have almost no ring lip at the top.

AaronSEIA

Posted By: DrAllis
Date Posted: 03 Feb 2023 at 5:54am

So, it's probably been overhauled once ?? It would be interesting to run a compression test on it. Might have been engineers first attempt at Power Crater piston bowl design, except not with a flat cylinder head.

Posted By: PaulB
Date Posted: 03 Feb 2023 at 6:42am

Compression on a BE/CE engine with dished pistons would be very low. To even get a reasonable 90-100 PSI requires the piston to be flat, because of the chamber in the head and come up to (or very near) the top of the sleeve at TDC. Not an attempt at Power-Crater pistons like used in the 20l-226 engines without a chambered head.

Better compression in a BE/CE engine requires domed piston or more stroke as was designed into the replacement for the BE/CE which was the 138/149/160 which has a flat, non chambered head.

Most likely with the "G" suffix suffix on the engine it was a low budget overhaul with used parts, or possibly something that dealer wanted to get rid of cheap. A kerosene engine (that would have left the factory with dished pistons) would have a "K" suffix.

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If it was fun to pull in LOW gear, I could have a John Deere.
Real pullers don't have speed limits.
If you can't make it GO... make it SHINY